1. Field of the Invention
The invention relates to new water-soluble, i.e. easily dispersible, amino-functional polyorganosiloxanes, which are obtained by radical polymerization of vinyl compounds containing amino or ammonium groups onto polyorganosiloxanes which contain at least one mercapto group, and which can be used as textile finishing aids.
2. Background of the Invention
From the literature, polyorganosiloxanes containing amino or ammonium groups have been known for a long time, and the most varied methods for their production have been described. As an example, reference will be made here to the synthesis of organopolysiloxanes containing tertiary amino groups as described by E. L. Morehouse in DE-OS 14 93 327, in which the desired compounds are obtained by hydrosilylation of methyl hydrogen siloxane.
As is known, for example, from U.S. Pat. No. 4,098,701, polysiloxanes which carry amino groups are suitable for finishing fiber material, in order to give such material the desired properties, such as a soft, smooth feel and wrinkle resistance. Therefore, these compounds are usually used as textile finishing aids.
In U.S. Pat. No. 4,098,701, polyorganosiloxanes which contain the grouping --(CH.sub.2).sub.3 NHCH.sub.2 CH.sub.2 NH.sub.2 as the amino-functional group are described. This grouping, however, causes a strong tendency toward thermal yellowing, a discoloration which is reinforced by elevated temperatures. To eliminate this problem, organopolysiloxanes which contain nitrogen, with side chains which do not contain any primary amino groups, were proposed in EP-A 0 692 567, for example. Furthermore, in EP-A 0 441 530, replacement of the amino ethylaminopropyl group with the N-methyl piperazino group was recommended, or, in EP-A 0 342 830, reaction of siloxanes containing amino ethylaminopropyl groups with butyrolactone was recommended.
The synthesis of modified siloxanes, for example by grafting ethylene-unsaturated compounds, such as styrene or methyl methacrylate, onto polydimethyl siloxanes containing mercapto groups (among others, DE 17 95 389 and U.S. Pat. No. 4,071,577) has been known for a long time. WO 94/14875 describes the synthesis of graft polymers on the basis of perfluoroalkyl acrylates and mercaptosiloxanes and their use as a water-repelling and oil-repelling finish for textiles.
Furthermore, in U.S. Pat. No. 4,985,155, a textile finishing aid on a silicone basis is described which is produced by polymerization of mercaptosiloxanes and alkyl acrylates or methacrylates, where up to thirty percent of the acrylates can be replaced by other acrylic acid derivatives, such as acrylamide or also dimethylaminopropyl acrylate. These products, which are insoluble in water, and demonstrate only low cationogeneity, are particularly suitable for soft coatings on textiles which are supposed to be water-proof and wind-proof, such as sports and ski clothing, raincoats, umbrellas, tents, and convertible tops. A proportion of at least 70 wt.-% of alkyl acrylates or methacrylates, however, is absolutely necessary in order to achieve a soft coating. A proportion below 70 wt.-% would impair the coating in such a way that bonding to the fiber surface is disrupted and satisfactory mechanical properties of the coating film are no longer obtained. In order to obtain an effective coating, a compound with a cross-linking effect (e.g. polyisocyanate) is used for the treatment. The weight proportion of the coating in the total weight of the coated textile is usually at least 20 wt.-%, but in some cases also significantly higher.
In the coating of flat textile structures as mentioned, the fabric to be coated is provided with a continuous layer, as free of pores as possible, of a water-repelling organic coating, in order to achieve not only surface hydrophobization but also penetration resistance to rain and water pressure resistance, for example for rain clothing. In this connection, the coating agent can be applied either on one side, by means of a device such as a ductor roller, or on both sides, for example by means of a foulard. The compounds used for coating can be present both as pastes which contain water, or dissolved in an organic solvent. Bonding of the coating masses to the surface of the textile takes place by means of added organic cross-linking agents, such as isocyanates, compounds which contain methylol groups or compounds which contain epoxy groups. The goal of this process is to structure the coating process in such a way that the greatest possible mechanical strength of the film is achieved, without causing overly great stiffening of the material. This is achieved by means of pre-hydrophobization of the textile to be coated, which prevents overly deep penetration of the coating mass into the woven material and, therefore, adhesion of the fibers to one another.
In high-grade finishing of textiles, significantly smaller amounts of finishing aids are used. Before being used in textile finishing, however, siloxanes first have to be converted into aqueous emulsions, which often requires a significant amount of effort. The usual emulsion processes, such as shear emulsification or emulsification by phase inversion, for the production of usable emulsions, are very complicated in technical terms and always represent a compromise between the stability of the emulsions which is necessary for commercial use and a deterioration of the application technology properties, such as a soft feel or resistance to rubbing of the treated textile substrate. This is caused by the addition of surfactants, co-surfactants or hydrotropics which is necessary for production of the emulsion. Another disadvantage of this form of preparation is the fact the silicone emulsions can be concentrated only up to a certain upper limit, without phase separations taking place or the emulsion solidifying into a paste which can be processed further only with difficulty. These disadvantages have had the result that until now, amino-functional siloxanes have been applied to the textile substrates almost exclusively by means of padding.
A large part of the softeners for textile substrates used in high-grade finishing, however, are applied using the drawing method. In order to be able to use a softener here, it must demonstrate not only great mechanical stability in the liquor, but also good stability with regard to pH deviations, the property of being easily dispersible or self-dispersible, as well as good drawing behavior and substantivity.
The task of the invention now consisted of making available amino-functional polyorganosiloxanes which are water-soluble or easily emulsified or self-emulsifying, and which can be produced economically, particularly using commercially available starting materials. It is supposed to be possible to use the amino-functional polyorganosiloxanes in aqueous formulations, as textile finishing aids or surfactants.